The grades on a geometry midterm at Gardner Bullis are normally distributed with $\mu = 79$ and $\sigma = 5.5$. Jessica earned a n $84$ on the exam. Find the z-score for Jessica's exam grade. Round to two decimal places.
A z-score is defined as the number of standard deviations a specific point is away from the mean We can calculate the z-score for Jessica's exam grade by subtracting the mean $(\mu)$ from her grade and then dividing by the standard deviation $(\sigma)$ $ { z = \dfrac{x - {\mu}}{{\sigma}}} $ $ { z = \dfrac{84 - {79}}{{5.5}}} $ ${ z \approx 0.91}$ The z-score is $0.91$. In other words, Jessica's score was $0.91$ standard deviations above the mean.